In recent years, a lot of research and development have been made on a mobility support in an IP layer such as Mobile IPv6 (Internet Protocol version6). The Mobile IP is a protocol of a network layer which is a third layer of the OSI (Open Systems Interconnection) Basic Reference Model established by the ISO (International Organization for Standardization), and is a technology for hiding movement of a client (switch of a network/communication medium, short break and the like) from higher-order applications so as to continue communication.
In TCP/IP (Transmission Control Protocol/Internet Protocol) which is a communication protocol generally used in the current internet generally, an IP address serves as an identifier and also shows a location on a network at the same time. Therefore, when a node connected to a certain network is reconnected to another network, an IP address thereof is changed and session is impossible to continue.
Hence, the Mobile IP provides a mechanism in which a unique address is assigned to a node and replaced with an IP address actually used in a TCP/IP stack, thereby it seems for upper layers or a communication partner that communication is performed with the assigned unique address in any network (for example, see Non-Patent Literature 1).
The Mobile IP is configured by nodes called a mobile node (Mobile Node, a mobile terminal, hereinafter, referred to as “MN”), a home agent (Home Agent, hereinafter, referred to as “HA”), and a correspondent node (Correspondent Node, a correspondent node, hereinafter, referred to as “CN”).
The MN has an always invariable address called a home address (Home Address, hereinafter, referred to as “HoA”), and a node that manages the address is the HA. When the MN is connected to a network other than a home link which is a link of the HA, an address actually used for communication that is called a care-of address (Care-of-Address, a care-of address, hereinafter, referred to as “CoA”) is acquired by some sort of means of, for example, a router advertisement (Router Advertisement, hereinafter, referred to as “RA”) of a stateless address auto-configuration, or a DHCP (Dynamic Host Configuration Protocol) v6 of a stateful address auto-configuration. The MN notifies the HA of the CoA acquired here with a message of Binding Update (Binding Update, hereinafter, referred to as “BU”).
As a result, when a node (=CN) to be desirably communicated with the MN sends a packet to the HoA, the HoA is an address of a link managed by the HA and is therefore temporally delivered to the HA. At that time, the HA transfers to the CoA associated with the HoA. As a result, the MN becomes always communicable by the HoA. In the MN, an application running on the MN always uses an IP address called the HoA above to communicate.
The CoA is used for a source address or a destination address of an actual IPv6 packet. Further, in order to hide movement from higher-order applications, technologies such as an IPv6 in IPv6 encapsulation and a mobility header are used. As a result, the HoA is notified to the application to hide an IPv6 address (CoA) actually used.
However, since this mobile IPv6 is incapable of performing a high-speed handover, FMIPv6 (Fast Handovers for Mobile IPv6) has been proposed (for example, see Non-Patent Literature 2).
With reference to FIG. 21 as an example, the FMIPv6 will be described.
An RtSolPr (Router Solicitation for Proxy Advertisement, a router solicitation proxy, hereinafter, referred to as “RtSolPr”) at S1201 in FIG. 21 is one in which a router solicitation (a router request) is extended for the FMIPv6, said router solicitation being a message sent by a host generally used in the IPv6 to a router to generate a router notification. The MN sends the RtSolPr to a PAR (Previous Access Router, an access router in communication, hereinafter, referred to as “PAR”).
Upon receipt of the RtSolPr from the MN, the PAR sends a PrRtAdv (Proxy Router Advertisement, a proxy router advertisement, Hereinafter, referred to as “PrRtAdv”) to the MN at S1202. The PrRtAdv is one in which an RA generally used in the IPv6 is extended for the FMIPv6.
Upon receipt of the PrRtAdv from the PAR, the MN sends an FBU (Fast Binding Update) that is a binding update for a high-speed handover to the PAR at S1203. The FBU includes NCoA (New Care of address, a new CoA, hereinafter, referred to as “NCoA”) information, and since the NCoA is an address belonging to a link of an NAR (New Access Router, an access router at a movement destination, hereinafter referred to as “NAR”), the PAR is capable of transferring a packet to the NAR.
Upon receipt of the FBU from the MN, the PAR sends an HI (Handover Initiate, hereinafter, referred to as “HI”) to the NAR to switch the MN and initialize a handover at 1204. The NAR sends, as confirmation for the HI, an HAck (Handover Acknowledgement, hereinafter, referred to as “HAck”) to the PAR at S1205, and packet transfer is started between the PAR and the NAR at S1206.
In addition, when the movement is finished and movement is completed to be under the control of the NAR (the same link), the MN sends an FNA (Fast Neighbor Advertisement, a high-speed neighbor advertisement, hereinafter, referred to as “FNA”) to the NAR at S1207. This is to notify the NAR of that the movement is completed. As a result, the NAR starts delivery of the packet to the MN at S1208.
In this method, it is stated that a tunnel between the PAR and the NAR in transition is created at the time of the handover, but a means for returning from a state in transition to a normal state is not mentioned.
The Mobile IP above performs mobility management by signaling driver from the mobile-terminal-side and is therefore called a mobility protocol on a host base. On the other hand, the IETF (Internet Engineering Task Force) has further proposed a network base IP mobility protocol, in which signaling for movement control is performed in the network side and the MN is capable of moving without a specific protocol for movement to be mounted (for example, see Non-Patent Literature 3).
This has such various advantages that the MN is not required to handle the CoA, an overhead due to a packet encapsulation or a mobility header is eliminated, and the like. A method for a handover of the network base IP mobility protocol will be described with reference to FIG. 22.
First, after the movement, at S1301, the MN sends an RS (Router Solicitation, a router request, hereinafter, referred to as “RS”) or a network configuration (network setting) request message such as a DHCP Request to a router of a link at a movement destination described as “NewMAG” in FIG. 22, a mobile access gateway (Mobile Access Gateway, hereinafter, referred to as “MAG”).
The MAG refers to a router that performs relaying between the MN moving to the link and a route router serving as a control apparatus for controlling an IP mobility, a local mobility anchor (Local Mobility Anchor, hereinafter, referred to as “LMA”).
The LMA controls a plurality of MAGs connected by a network. The LMA manages identifiers of the MN and MAG and IP addresses in a storage portion.
The MAG also manages identifiers of the MN and LMA and IP addresses in a storage portion. The information managed by the MAG can be acquired by performing communication with the LMA.
By performing IPv6 in IPv6 encapsulation of a packet and adding a header with reference to information stored in the storage portion, tunneling is performed between the MAG and the LMA so that routing can be performed properly.
In the network as described above, the MN sends, here, for example, the RS to the MAG in the same link at a movement destination. Upon receipt of the RS from the MN, the MAG (NewMAG) sends a location registration (location registration request) to the LMA at S1302.
Upon receipt of the location registration, the LMA detects as a handover, and, at S1303, sends a routing set-up to the MAG (NewMAG) and sets a tunnel path between the NewMAG and the LMA.
Setting of the tunnel path means to set so that a packet for the MN is encapsulated in the LMA, sent to the MAG (NewMAG), decapsulated in the MAG, and then transferred to the MN.
Upon receipt of the routing set-up, the MAG (NewMAG) sends a routing set-up Ack for confirmation to the LMA at S1304.
Further, upon receipt of the location registration from the MAG (NewMAG), the LMA sends a location registration Ack for confirmation to the MAG (NewMAG) at S1305.
At S1306, the MAG (NewMAG) sends an RA to the MN and the MN performs an address configuration (address setting).
Thereafter, at S1307, the MN performs a DAD (Duplicate Address Detection, a duplicate address detection, hereinafter, referred to as “DAD”) with respect to the MAG (NewMAG) using an NA (Neighbor Advertisement, a neighbor advertisement, hereinafter, referred to as “NA”), and confirms that the address is single to complete the address configuration. Further, the MAG (NewMAG) sends an MN address set-up to the LMA at S1308, and the LMA sends an MN address set-up Ack to the MAG (NewMAG) at S1309.
As a result that the tunnel path is set between the LMA and the MAG and the address configuration in the MN is completed, the packet is reachable to the MN. This is a method for the handover of the network base IP mobility protocol. That is, since a packet addressed to the MN is sent through the LMA, by completing a tunnel between the LMA and the MAG, routing to the MN is possible.    Non-Patent Literature 1: Request for Comments (RFC) 3775, “Mobility Support in IPv6”    Non-Patent Literature 2: Request for Comments (RFC) 4068, “Fast Handovers for Mobile IPv6”    Non-Patent Literature 3: Internet Draft “draft-giaretta-netlmm-dt-protocol”